Interfacial Welding of Sulfur-Containing CNTs for an Elastic and Conductive Hydrogel with High-Accuracy Motion Sensing and Electrophysiology Acquisition

Elastic hydrogels with conductive nanofillers are promising candidates for acquiring multifunctional biological signals when adhered to human skin. However, conductive hydrogels are frequently ruptured due to their weak mechanical characteristics, especially withstanding plaguily stretching. Herein, we present a highly elastic, low-hysteresis, conductive poly(acrylic acid)/polyacrylamide (PAA/PAM) hydrogel with sulfur-containing carbon nanotubes with abundant graphene nanoflaps (S-CNTs). Sulfur atoms in situ form covalent bonding with PAM polymer chains, while graphene nanoflaps established a mechanical interlocking interface, which strongly improved the mechanical robustness of the hydrogel network with conductive nanofillers. As a result, the S-CNTs/PAA/PAM hydrogel exhibits comprehensive mechanical properties with a superior stretchability of >1200%, lower hysteresis (7.4%), and excellent mechanical durability (>600 cycles). Therefore, the S-CNTs/PAA/PAM hydrogel was utilized as an epidermal electrode for dynamically monitoring human daily motions and electrophysiological signals. We believe that this work paves the way for the potential application of flexible/wearable electrodes and maybe even integrating both into the same device for human health detection in the future bioelectronic systems.